QUIC: keep stream sockaddr and addr_text constant. HTTP and Stream variables $remote_addr and $binary_remote_addr rely on constant client address, particularly because they are cacheable. However, QUIC client may migrate to a new address. While there's no perfect way to handle this, the proposed solution is to copy client address to QUIC stream at stream creation. The change also fixes truncated $remote_addr if migration happened while the stream was active. The reason is addr_text string was copied to stream by value.